1. Field of the Invention
The present invention relates to a communication method which is applied to a case in which data transmitted via a cable-communication channel is transferred via a wireless communication channel, and relates to a communication apparatus to which the communication method is applied.
2. Description of the Related Art
As a conventional communication method among a plurality of apparatuses for exchanging data having a relatively large amount of information such as digital image data, computer programs, and file data, one using an IEEE-1394 high-speed serial bus interface has been developed. The IEEE-1394 high-speed serial bus interface allows packet-structured data to be transmitted to a desired apparatus from among a plurality of apparatuses which are connected to the serial bus for data communication.
Data communication using the IEEE-1394 high-speed serial bus interface offers two communication modes: one is an isochronous communication mode for successively transmitting the data having a relatively large amount of information such as image data; the other is an asynchronous communication mode for randomly and reliably transmitting data having a relatively small amount of information such as control data.
Data communication using the IEEE-1394 high-speed serial bus interface enables various data to be exchanged among the apparatuses connected to the serial bus line.
Generally, when a wireless communication frame is established, the wireless communication frame is established so as to have a communication period which is greater by several orders of magnitude than the period of a cable-environment communication cycle (approximately a 125 xcexcs unit), that is, for example, a 4 ms unit. Since conversion processing for converting cable-environment data into a communication signal formatted for a wireless-environment and other coding and decoding processing require some time, the wireless communication frame depends on the operating times of various control apparatuses. Therefore, it is difficult to perform data communication via the wireless communication channel without directly converting the cable-environment data.
When being performed in the cable environment, it is required that a band having a size corresponding to the amount of transmission is established beforehand and the isochronous communication is performed so that the amount of transmission does not exceed the established band. Likewise, when being performed in the wireless environment, it is required that a band for wirelessly transmitting data is reserved and the isochronous communication is performed so that the amount of transmission does not exceed the reserved band. In addition, when the isochronous communication is performed in the cable environment, an isochronous packet is transmitted every communication cycle (approximately a 125 xcexcs unit).
When the isochronous information transmitted via the cable environment is transmitted via the wireless communication channel, a wireless communication apparatus on the sending side transmits information via the wireless communication channel in which the isochronous information arranged in units of communication cycles is packed in units of communication frames (for example, 4 ms unit) in the wireless environment. A wireless communication apparatus on the receiving side reconstructs the isochronous information in units of communication cycles in the cable environment.
In the cable-environment isochronous communication, the amount of information can be variable during one communication cycle in the cable environment. That is, the entirety, a half, or none of the reserved band which is occupied by the isochronous information can be transmitted during every cycle.
Accordingly, the wireless communication apparatus on the sending side must inform the other apparatus on the receiving side of how often and how much cable-environment isochronous information is contained in a wireless-environment packet which contains isochronous packets corresponding to a plurality of cable cycles. Such information processing becomes redundant over a long period of the isochronous transmission.
In view of the foregoing problem, a first object of the present invention is to provide a wireless communication method which guarantees the equivalent communication band in cable-environment isochronous communication because, before transmitting isochronous information via a wireless channel, a band required for wireless communication can be reserved and can be used exclusively for wireless communication.
It is another object of the present invention to provide a wireless communication method which enables stable isochronous communication to be performed by informing corresponding communication apparatuses on both sending and receiving sides of information on the communication band used for the wireless communication before isochronous information is wirelessly transmitted.
It is a further object of the present invention to provide a wireless communication method which enables communication bands to be repeatedly used by releasing a corresponding reserved communication band at the end of the isochronous communication.
To this end, according to a first aspect of the present invention, there is provided a wireless communication method for a control station which controls a wireless network including the control station and at least one communication station. The wireless communication method comprising the steps of receiving a communication band reservation request from a communication station which desires to perform isochronous communication, assigning a wireless communication band for the communication station and notifying the band assignment to the communication station when the band can be reserved, and allowing the communication station to perform isochronous communication using the assigned wireless communication band when the band can be reserved.
According to a second aspect of the present invention, there is provided a wireless communication method for a communication station used in a wireless network comprising a control station and the communication station. The wireless communication method includes the steps of transmitting to the control station a band reservation transmission request transmitted from a terminal connected thereto via a high-speed serial bus, receiving a communication band assignment notification from the control station, and performing isochronous transmission in the communication band assigned in accordance with the communication band assignment notification.
According to a third aspect of the present invention, a wireless communication apparatus includes a wireless reception unit for establishing a predetermined wireless communication data structure and receiving wireless communication band assignment information, a cable reception unit for receiving isochronous communication information transmitted from various devices connected thereto via a high-speed serial bus, an information converting unit for converting the isochronous communication information into data information arranged in units of blocks based on a predetermined format established in accordance with the wireless communication band assignment information, and a wireless transmission unit for wirelessly transmitting the data information.
According to a fourth aspect of the present invention, a cable communication apparatus includes a first wireless reception unit for establishing a predetermined wireless communication data structure and receiving wireless communication band assignment information, a second wireless reception unit for receiving data information transmitted via a predetermined wireless communication channel, an information converting unit for converting wireless communication data information arranged in units of blocks based on a predetermined format established in accordance with the wireless communication band assignment information into periodical cable-environment isochronous communication information, and a cable transmission unit for transmitting the isochronous communication information to various devices connected thereto via a high-speed serial bus.
According to a fifth aspect of the present invention, a wireless communication apparatus includes an information detecting unit for detecting isochronous communication band reservation information transmitted from various devices connected thereto via a high-speed serial bus, a first wireless transmission unit for wirelessly transmitting, to a wireless communication apparatus serving as a control station, a request for acquiring a wireless communication band required for wireless communication based on the detected isochronous communication band reservation information, a wireless reception unit for establishing a predetermined wireless communication data structure and receiving wireless communication band assignment information, a cable reception unit for receiving isochronous communication information transmitted from various devices connected thereto via the high-speed serial bus, an information converting unit for converting the isochronous communication information into data information arranged in units of blocks based on a predetermined format established in accordance with the wireless communication band assignment information, and a second wireless transmission unit for wirelessly transmitting the data information.
According to a sixth aspect of the present invention, a cable communication apparatus includes a wireless reception unit for establishing a predetermined wireless communication data structure and receiving wireless communication band acquiring request information transmitted from a wireless communication apparatus, a first wireless transmission unit for wirelessly transmitting wireless communication band assignment information based on the wireless communication band acquiring request information, a cable reception unit for receiving isochronous communication information transmitted from various devices connected thereto via the high-speed serial bus, an information converting unit for converting the isochronous communication information into data information arranged in units of blocks based on a predetermined format established in accordance with the wireless communication band assignment information, and a second wireless transmission unit for wirelessly transmitting the data information.
According to a seventh aspect of the present invention, a cable communication apparatus includes a first wireless reception unit for establishing a predetermined wireless communication data structure and receiving wireless communication band acquiring request information transmitted from another wireless communication apparatus, a wireless transmission unit for wirelessly transmitting wireless communication band assignment information based on the wireless communication band acquiring request information, a second wireless reception unit for receiving data information transmitted via a predetermined wireless communication channel, an information converting unit for converting the wireless communication data information arranged in units of blocks based on a predetermined format established in accordance with the wireless communication band assignment information into periodical cable-environment isochronous communication information, and a cable transmission unit for transmitting the isochronous communication information to various devices connected thereto via a high-speed serial bus.